Abstract
Much ecological research relies on existing multispecies distribution datasets. Such datasets, however, can vary considerably in quality, extent, resolution or taxonomic coverage. We provide a framework for a spatially-explicit evaluation of geographical representation within large-scale species distribution datasets, using the comparison of an occurrence atlas with a range atlas dataset as a working example. Specifically, we compared occurrence maps for 3773 taxa from the widely-used Atlas Florae Europaeae (AFE) with digitised range maps for 2049 taxa of the lesser-known Atlas of North European Vascular Plants. We calculated the level of agreement at a 50-km spatial resolution using average latitudinal and longitudinal species range, and area of occupancy. Agreement in species distribution was calculated and mapped using Jaccard similarity index and a reduced major axis (RMA) regression analysis of species richness between the entire atlases (5221 taxa in total) and between co-occurring species (601 taxa). We found no difference in distribution ranges or in the area of occupancy frequency distribution, indicating that atlases were sufficiently overlapping for a valid comparison. The similarity index map showed high levels of agreement for central, western, and northern Europe. The RMA regression confirmed that geographical representation of AFE was low in areas with a sparse data recording history (e.g., Russia, Belarus and the Ukraine). For co-occurring species in south-eastern Europe, however, the Atlas of North European Vascular Plants showed remarkably higher richness estimations. Geographical representation of atlas data can be much more heterogeneous than often assumed. Level of agreement between datasets can be used to evaluate geographical representation within datasets. Merging atlases into a single dataset is worthwhile in spite of methodological differences, and helps to fill gaps in our knowledge of species distribution ranges. Species distribution dataset mergers, such as the one exemplified here, can serve as a baseline towards comprehensive species distribution datasets.
Highlights
Large-scale species distribution data are widely used in macroecology, for example to determine richness patterns in biogeographical studies [1], to estimate species abundances [2], to fill data gaps in monitoring programmes [3] or to assess priority areas for biodiversity conservation [4,5]
Distribution data obtained from existing atlas datasets or from an open access data publishing framework such as the Global Biodiversity Information Facility database, vary considerably in data quality, their spatial extent, spatial resolution and taxonomic coverage [6]
Species Richness After taxon updating and exclusion of records for extinct species, the Atlas Florae Europaeae (AFE) data set contained records for 3773 taxa (27% of the original taxa needed some form of nomenclatural updating or editing)
Summary
Large-scale species distribution data are widely used in macroecology, for example to determine richness patterns in biogeographical studies [1], to estimate species abundances [2], to fill data gaps in monitoring programmes [3] or to assess priority areas for biodiversity conservation [4,5]. Large-scale comprehensive species distribution datasets are remarkably scarce [3,4,11,12,13] This gap is most noteworthy for vascular plants in Europe, given the continent’s long history of botanical research. A possible sampling bias in this occurrence atlas is, a systematic over-representation of plant species in northern, western and central Europe as volumes covering important Mediterranean families are not published yet [24]. Another problem of AFE is that sampling intensity varies among countries [25], the extent of this variation is not known
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